Q. I did an oil painting several years ago using a medium made from equal parts stand oil, damar varnish and turpentine. Should the final varnish coat be compatible with the medium (such as damar varnish) or is there a better choice?

A. Yes, the final varnish ought to be compatible with the paints and mediums you’ve used. Damar resin, however, has pretty much been discredited as a surface coating for paintings. It cracks, and as it ages it yellows and becomes harder to remove. There are now much better varnishes for this purpose, and I can recommend two.

The acrylic-solution varnishes, such as Golden Artist Colors’ MSA (which also contains an ultraviolet light absorber), are a good alternative to natural resin varnishes. They’re thinned with mineral spirits and applied in the same manner as damar varnish. Winsor & Newton and Liquitex make acrylic-solution varnishes as well.

There’s also a relatively new product developed by Gamblin Artist Colors and conservation scientists at the National Gallery of Art. Called Gamvar, it includes separate jars of a styrene resin and a mineral spirits solvent. You mix the two parts and use it within a month. The advantage over acrylic-solution varnishes is that Gamvar has a lower molecular weight, which makes it easier to remove as it ages.

You mentioned that your painting is several years old. Before you varnish it, be sure the surface is thoroughly cleaned by lightly dusting it with a soft brush. Then gently wipe it with a soft, white, cotton rag, slightly dampened with mineral spirits, to remove any residual dirt. If you notice any color on the rag, stop at once: You may be removing some underbound paint. In that case, the dust removal alone will have to do.

By the way, that’s not a bad medium you used, but I recommend for the future that you reduce the amount of damar in it to about 10 percent of the total volume (compensate by increasing the amount of gum turpentine). That way, the paint layers will be less susceptible to solvents should the painting ever need to be cleaned.

Artist and instructor Butch Krieger is a contributing editor for The Artist’s Magazine. He lives in Port Angeles, Washington.